Indigo dyestuff



ration 0 indoxyl to indigo has a direct bearing on the condition underwhich the dye is ob- Patented June 15, 1926.

UNITED STATES ATEN OFFICI-I INDIGO DYEQTUFI.

in Drawing.

This invention relates to a simple method 3f producing a dye stuflconcerning indigo At the present time the production of the above hasbeen brought about by several well known methods. re resented by theempirical formula G NO, but in reality the formula is more complicatedas by an analysis of the vapor density of indigo blue, it has been foundthat the formula must be double that of the empirical formula justmentioned, and is consequently (OJ-1 01i) The empirical- QK CI! 0 O BIOOH HO 0 0 HO OH HO OH:

0 Indolo Indoxyl OH a o o oo 00 on:

i. +03 0H, mo on or o The relation of indoxyl and isatin' to indigo wasestablished by Von Bayer and his pupils, forming the basis for the mostim' portant s nthetical methods for the prepa the dye, whilst therelation of tained from theindigo plant.

The dye is usually.

Application an my m, 1924. Serial m. water.

formula of the indigo blue has been changed from time to time as newfacts have been ascertained, and the present formula is the result ofexperimentation in which the fol lowing facts were gathered:

1. The presence ofa benzene rin in the molecule as shown by its easyoxidation into isatin which contains the ring.

2. The ease withwhich indigo is obtained from indole, indoxyl, and:isatin, being the evidence of the fellows:

presence of the structure as From the summary of all the'availablederivatives of indigo or analogues of the substances, the followingfacts are obtained, that the tinctorial properties of indigo are due tothe presence of the chromophore group i which forms a closed chain withthe benzene ring.

But the present invented method em- -ployed produces a dyestuii ,o 1itsanalogues indigo blue direct Irorn--aniline' iidtthrough the Line'ofHeumanns' synthesis obtained through phenyl-glycccoll by thecondensation of aniline with chloracetic acid, nor by the application offormaldehyde and sodium cyanide to aniline. It brings out another factthan the above- I I 1. That the tinctorial power of the indigo or itsanalogues resides not on linking car on atoms with a closed cneinformingthe henzene ring as shown above, but on the aniline itself asshown below;

N e, @1 1 other chromic oxides or potassium dichromate can he used foroxidizing the aniline 111 the above manner.

Note: Other peroxides can b'used for oxidizing the aniline in the somemanner.

III. The aniline can be oxidized inthe same way ifsodium eroxide,otassium chlorate, calcium hypociilorite or leaching powder is used,only in the case of the latter,

t little calcium peroxide is needed to aid the reaction to completion.

That is, when aniline is oxidized by means of oxides, peroxides ortrioxides, etc, with the aid of inorganic acid, the blue chromohore isformed us a fundamental part of indigo, but I have stated already thatindigo contains a bonded chain of C()-G:G-OC groups linked with abenzene ring which gives the following formula corresponding to thevapor density.

(kl-Anti...

50 OH H0 OH That is, when a substitution product is attached tothechromophore blue, complete indigo synthesis is obtained; and s littingthe indigo Withpotassium hydroxi e, two

products are noticed. One is aniline, which is already known to thechemists of indigo, but the other was not very closely observed whenaniline was distilled. over.-

The process and the product on the other hand were not thoroughlyiuvestigutml lee- .fore. The product appears to me altcr ceregroup withthe euroinophore blue, o? o dye is obtained with a vapor density use fulanalysis to resemble pot issium acetate in properties. in attachingsciatica/aid a substitution of the 4 indigo blue.

In In opinion, the tinctoriei power indigo ies within the imino he zenering. As there is only C-OC:C---@C inolmulee needed besides theiminohenzene ring to complete the indigo formula, is attained by theaddition of organic acids- To prove this, experiment has been withchromophore blue and other organic acids, such'os acetic-citric,gene-formic (grailie and formic}, laeto-iormio {hectic and nmic),oxalic, tennic, tartaric, etc, and

blue indigoid is obtained according as the required substitution Ctiiqfl -fili she a would he required from the above organicacids or theircombinations, The above formulas will set in the. saris-a wuy if anilinehydrochloride is used iw stead of aniline, only additional chloric acidmust he added to term the e pounds, such as in thecase 01? Eechorgnnicacid will form. iudig in the above mentioned processes in neon chromehere blue is formed, some or the: being siown here below: I

1.-A:-iiliue, hydrochloric acid, acetic and chromic trzoziido- --indigocipitated by alkali metal hydroxide 2.-.'ihe above formula with Na i),instead of chroniic tricside,

3.The above formula with ICKS tinsteed of the above oxidizing s5 tr-Theaboi e forruul with Suit", in of the shove oizidizi. lir -The abovefQX'H'm with CREE, l of the above uxidizin 6=--The chore use. pochloriteor bleeehi the above oxidising i. i 1

The alcove Wili reset; in the some i citric, gailmformie, loom-formic,or nie, tartaric, etc, orgeuic acids, are substitute the i wo ci-cogroup. @r in other WOTClS, i'ncii' o ormed if aniline isOX'ifiilZBCl end acids used to substitute 2 The method of making indi ocompris- 16 ing treating chromophorei'blue aving. the

formula.

. w mn o.n. 115 NH raiiical is attached to the imino benzene rings ofthe chrome hore blue.

3. The method 0 making indigo comprising oxidizing aniline in acidsolution to prey 413100 chromophore blue having th s formula.

"radical to the .iniin'o benzene rings ofthg chrome hoz e blue bytreating the chromq v phore b ue with an organic anld.

sAILnND N. (iUfiTAc 1

